Diffraction imaging by multifocusing

Abstract

Correct identification of geologic discontinuities, such as faults, pinch-outs, and small-size scattering objects, is a primary challenge of the seismic method. Seismic response from these objects is encoded in diffractions. Our method images local heterogeneities of the subsurface using diffracted seismic events. The method is based on coherent summation of diffracted waves arising in media that include interface discontinuities and local velocity heterogeneities. This is done using a correlation procedure that coherently focuses diffraction energy on a seismic section by flattening diffraction events using a new local-time-correction formula to parameterize diffraction traveltime curves. This time correction, which is based on the multifocusing method, depends on two parameters: the emergent angle and the radius of curvature of the diffracted wavefront. These parameters are estimated directly from prestack seismic traces. The diffraction multifocusing stack (DMFS) can separate diffracted and reflected energy on a stacked section by focusing diffractions to the diffraction location and defocusing the reflection energy over a large area.

Enhancement of prestack diffraction data and attributes using a traveltime decomposition approach

“…Geophys. Geod., 60 (2016) workflows with the goal to separate diffractions from reflections and to enhance diffractions in the post-stack domain have been presented (Fomel et al, 2007;Berkovitch et al, 2009;Dell and Gajewski, 2011). However, an important goal of diffraction imaging is the separation of diffractions and their enhancement in the full prestack data volume, which requires finite-offset (FO) processing.…”

Coal seismic diffraction fault imaging: Results from numerical modelling

“…transform) for separating diffractions from reflections for velocity estimation on post-stack sections. Khaidukov et al (2004) and Berkovitch et al (2009) extracted the diffractions by muting the focused imaginary source points from reflections on a prestack shot gather. Taner et al (2006) used plane-wave destruction filter to suppress reflections and retain diffractions.…”

High-resolution imaging of diffractions — A window-steered MUSIC approach

“…From an imaging point of view, Moser and Howard (2008) use antistationary filtering to separate reflective and diffractive components during the migration, while Zhang (2004) performs prestack depth diffraction imaging using the idea of the Fresnel aperture. Diffraction enhancement can also be carried out using MF (Berkovitch et al, 2009) or the CRS (e.g., Asgedom et al, 2011b;Dell and Gajewski, 2011) stacking methods. In this work, the CRS approach has been applied, in which a modified version of the CRS moveout, better tailored for diffractions, is used.…”

“…More recently, much attention has been paid to the enhancement and separation of diffractions from reflection data for many imaging purposes. Several approaches have been proposed, among them the use of antistationary filtering (Moser and Howard, 2008), plane-wave destruction filters (Fomel et al, 2007), multifocusing (MF) (Berkovitch et al, 2009), or the common reflection surface (CRS) (Asgedom et al, 2011a(Asgedom et al, , 2011b(Asgedom et al, , 2012a(Asgedom et al, , 2012b stacking methods. Because the diffracted events are known to carry high-resolution information about the subsurface, their optimal use in imaging is an important topic.…”